Introduction It is well known that insulin-like growth factor-1 (IGF-1) is an effective osteoporotic growth factor, which increase dramatically during puberty, augmented by the increasing levels of sex steroids, and positively affects bone turnover by stimulating osteoblasts proliferation and differentiation (Davies et al., 2005). Bone mineralization increases with age, height, and body mass increase throughout childhood, with a significant gain during pubertal development, resulting in an increase of BMD of about 40% during this period (Gordon, 1991). The aim of this cross-sectional study was to evaluate the relationships between BMD and IGF-1 in adolescent female athletes. Methods The participants were eighty 13-15 year-old girls comprising three groups: gymnasts (n=23), sprinters (n=24) and controls (n=33). Body height and body mass were measured, and body mass index (BMI) was calculated (kg/m2). BMD at lumbar spine (L2-L4) and femoral neck (FN) were measured by DXA. Morning fasting blood samples were collected for analysis of IGF-1 and IGFBP-3, and IGF-1/IGFBP-3 molar ratio was calculated. For those girls who had menarche, the fasting blood samples were drawn on early follicular phase of the menstrual cycle. Results Gymnasts BMD FN was significantly higher than sprinters and controls (1.13 ± 0.15 vs. 1.05 ± 0.09 and 1.01 ± 0.11 g/cm2, respectively). The levels of IGFBP-3 were significantly greater in gymnasts than in sprinters (6.0 ± 0.7 vs. 5.5 ± 0.7 mg/L, respectively). There were significant correlations of IGF-1 and IGF-1/IGFBP-3 molar ratio with BMD FN and L2-L4 (r = 0.39-0.59) in gymnast and control groups, but not in sprinters. After adjusting for age, body height and body mass, the significant correlations between IGF-1 and BMD variables (r = 0.49-0.52) were revealed in gymnast group only. Stepwise multiple regression analysis indicated that BMD FN and L2-L4 were influenced by IGF-1 up to 31.0-34.6 % (R2x100) in gymnasts, and by IGF-1/IGFBP-3 - up to 19-32 % (R2x100) in controls. Discussion In our study, no significant differences between the groups were found in respect to IGF-1 levels and IGF-1/IGFBP-3 ratio, but BMD FN was significantly greater in gymnasts. Previously, IGF-1/IGFBP-3 was indicated as the most robust predictor of femoral neck BMD in young adult women with different physical activity patterns (Snow et al., 2000). This corresponds well with our research findings, although the significant relationships of BMD FN and L2-L4 with IGF-1 levels and IGF-1/IGFBP-3 ratio were found in pubertal gymnast and controls, but not in sprinters. We conclude that IGF-1 is strongly correlated with BMD FN and L2-L4 in adolescent gymnasts, but not sprinters.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Veröffentlicht von The Norwegian School of Sport Sciences. Alle Rechte vorbehalten.